Tear tape for plastic packaging materials



Aug. 3, 1968 M. B. LUCAS 3,396,900

TEAR TAPE FOR PLASTIC PACKAGING MATERIALS Original Filed Dec. 24. 1964Fig. l

INVENTOR. Malcolm B. Luccs ATTORNIEY United States Patent O ABSTRACT OFTHE DISCLOSURE A tear tape is adhered to the outer surface of a plasticpackage by the use of a hot-melt adhesive composition applied on anarrow elongated area of the outside surface of the plastic packagingmaterial. The package is opened by pulling on one end of the tear tapewhich causes the plastic packaging material to tear along the edges ofthe adhered area.

This application is a division under Rule 147 of copending patentapplication filed Dec. 24, 1964, Ser. No. 420,974, now US. Patent No.3,311,032.

This invention relates to the art of plastic packages and moreparticularly, to the provision of a tear tape for packages made fromplastic packaging films as Well as a method of applying tear tapes tosuch packaging films.

The formation of packages from plastic film materials such aspolyethylene, polypropylene and the like, has become one of the mostcommon methods of packaging articles for sale in the retail trade. Inspite of the many millions of pounds of plastic film materials usedannually to package articles of all kinds, the art has lacked auniversally satisfactory tear tape device applicable to virtually anyplastic packaging film material and one which can be applied atcommercially feasible packaging machine speeds.

For example, it has been proposed to heat seal a tear tape to theoutside surface of a packaging material formed from a plastic filmhaving thermoplastic properties. This can be accomplished but usually atthe expense of thinning and/ or weakening the packaging material itself.On the other hand, if the packaging material is neither thinned norweakened, the heat seal approach limits the application of the tape to aparticular direction with respect to the grain orientation in the parentfilm material if clean straight tears are desired. Additionally, thebonding of tear tapes solely by heat and pressure is a relatively slowprocess that does not lend itself easily to high speed productionmethods as commonly encountered in present day commercial packagingpractices in order to operate on a competitive basis.

It is, therefore, a principal object of this invention to overcome allof the above-stated difiiculties.

Another object of this invention is the provision of a tear tape for aplastic packaging film which can be applied to the external surface ofthe packaging film without weakening or thinning the parent packagingmaterial.

A further object of the invention is to apply a tear tape on the outsidesurface of a plastic film packaging material that will satisfactorilytear open the packaging material regardless of the grain orientation inthe parent film material with respect to the long dimension of the teartape itself.

Still a further object of this invention is the provision of a method ofapplying a tear tape by means of hotmelt adhesive whereby tear tapes canbe intermittently adhered to a continuous plastic packaging film at therate of at least 300 tear tapes per minute.

The nature and substance of the invention can be summarized briefly asthe provision of a package made from a plastic packaging film forenclosing at least one article and having a tear tape adhered thereto.The tear tape is adhered to the outer surface of the plastic packagingfilm by means of a hot-melt adhesive which is applied so that it forms anarrow elongated adhered area on the outside surface of the packagingfilm. The plastic packaging film can be formed around any article inmaking a package, and the tear tape may be adhered to the plastic filmeither before or after the package is formed. The package is openedsimply by pulling on the tear tape so that the pulling force causes theplastic packaging film to be severed along the edges of the adhered areato allow access to'the package contents.

While the specification concludes with claims particularly pointing outand distinctly claiming the subject matter regarded as forming thepresent invention, it is believed the invention will be betterunderstood from the following description taken in connection with theaccompanying drawing in which:

FIGURE 1 is a diagrammatic view of an apparatus for practicing themethod of applying tear tapes at spaced intervals on a continuouslymoving plastic packaging film.

FIGURE 2 is a fragmentary view of the plastic packaging film after ithas had tear tapes applied intermittently thereto.

- FIGURE 3 is a cross section taken on the line 3-3 of FIGURE 2 showinga tear tape bonded to the plastic packaging film.

FIGURE 4 is an elevation of a package made from the film shown in FIGURE2 showing the side of the package opposite to the tear tape.

FIGURE 5 is a perspective of the package of FIGURE 4 showing the teartape side.

FIGURE 6 is a view similar to FIGURE 5 wherein the tear tape is shownwhen it has partially opened the package.

FIGURE 7 is a view similar to FIGURE 6 showing the package after thetear tape has completed tearing an opening in the package so that thecontents of the package are accessible.

FIGURE 8 is a fragmentary cross section taken on the line 88 of FIGURE 3showing the pattern of the adhesive material as applied to the plasticpackaging fil-In.

In utilizing the present invention, it has been found practical to applytear tapes continuously at spaced intervals to a web of plasticpackaging film material prior to the formation of the film into asuccession of inindividual packages. The invention has equal merit andutility, however, when the tear tapes are individually applied tofinished packages. Nevertheless, the application of the tear tapes tothe continuously moving packaging film is considered of greaterpractical importance since this permits the adherence of tear tapes tothe film at speeds in excess of 300 tear tapes per minute. Such a speedis substantially greater than the speeds that have been possible withprevious known methods of applying tear tapes.

FIGURE 1 schematically illustrates the manner in which the tear tapescan be applied continuously to a web of plastic packaging material. Acontinuous web of plastic film material is withdrawn from the supplyroll 10. The material stored on the supply roll 10 may be a plastic suchas polyethylene, polypropylene, polyvinylchloride or any of the otherplastic films which find widespread use in the packaging art. The Web 12withdrawn from the supply roll 10 is led over the idler rolls 14, 16, 18and 20 to the recessed roll 22.

A solid hot-melt adhesive material 24 is fed in cordlike form from thespool 26 to the applicator 28. The adhesive is liquified in theapplicator 28 by suitable heating means. The liquified adhesive ispicked upby the applicator wheel which is normally rotated continuouslyso that its peripheral surface moves in the same direction as thedirection of movement of the web 12. The peripheral surface of the Wheel30 is greater than the speed of the moving Web 12. The applicator wheel30 is narrower than the overall width of the tear tapes which areadhered to the web 12 at spaced intervals.

The roll 22 is recessed at 32 and 34 so that the adhesive is applied ina narrow elongated area at spaced intervals on the web 12 as it passesover the high portions 36 and 38 of the roll 22. When either of therecessed portions 32 or 34 are in juxtaposition to the applicator wheel30, the tension in the web 12 is such that the web 12 follows thesmaller diameter of the recesses thereby causing the web 12 to breakcontact with the applicator wheel 30.

A supply roll of tear tape material 40 is provided. A web of tear tapematerial 42 is continuously withdrawn from the supply roll 40. The teartape material may be composed of a laminate of several different plasticmaterials or it can be made of a non-plastic woven or unwoven fabric orvirtually any of the common plastic materials such as polyethylene,polypropylene, etc. By way of example, it has been found that a laminatecomposed of polyethylene terephthalate, polyvinylidene chloridecopolymer, and polyethylene is very satisfactory although it should beunderstood that the exact composition of the tear tape is not criticalto the present invention.

The tear tape material 42 is led under the idler roll 44 and is fedforward by the metering wheels 46 and 48 to a slip-drag vacuum wheel 50.The slip-drag vacuum wheel 50 rotates continuously and causes the tapeto adhere thereto by means of an internal vacuum. The wheel 50 isrotated so that its surface move-s at about twice the speed of themoving tear tape material 42. A rotary cutoff knife 52 cuts individualtapes from the web 42. The wheel 50 is provided with oppositely disposedanvils 54 and 56. In addition, grooves 5 8 and are provided. The grooves58 and 60 are of diminishing depth leading from the anvils 54 and 56,respectively, to a point on the surface of the wheel 50 intermediate theanvils. The width of grooves 58 and 60 is such as to contain the teartape material 42 and prevent lateral movement on the wheel 50. Inaddition, the grooves 58 and 60 serves as a guide for the free end ofthe tape material until a sufiicient length has been withdrawn and isproperly held against the slip-drag vacuum wheel 50.

The rotational speed of the wheel 50 is such that a tape will be cut offat the anvil 54 when the leading end of the tape is at the end 61 of thegroove 60. The leading end of the Web 42 will then slip in the groove 58of the wheel 50 so that the next tape will have its leading end at theend 62 of the groove 5-8 when the tape is severed from the web at theanvil 56. Thus, as the wheel 50 is rotated, individual tear tapes aresevered for application at spaced intervals on the web 12.

The rotation of the slip-drag vacuum wheel 50 is synchronized with therotation of the recessed roll 22 so that a tape is delivered to the web12 between the roll 63 and the wheel 50 coincidentally with the arrivalof a length of web 12 to which a narrow elongated stripe of adhesive hasbeen applied. An internal air jet 64 is provided opposite the wheel .12which blows each successive tear tape from the wheel 50 and causes it tobe applied against the adhesive stripe on the web 12 whereupon it isproperly adhered when the adhesive solidifies. With some tape materialsit may be desirable to use a pressure roll 65 having a nip 66 with theroll 63. This is particularly desirable when fabric tapes are used inorder to get sufficient penetration of adhesive into the fabric tapematerial. The finished web is fed over the idler roll 67 and is led fromthere to any suitable location such as a rewind stand or a packagingmachine which immediately uses the web material.

FIGURE 2 illustrates the finished web showing in-- dividual tear tapes68 and 70 applied thereto. It will be noted byreferring to FIGURES 3 and8 that the length of the bond '72 is somewhat less than the total lengthof the tape 68. This leaves a free end or pull tab 74 which can begrasped and pulled to apply the necessary tear force to sever theplastic packaging material. The arrow A in FIGURE 2 denotes thedirection of movement of the web 12 when tear tapes are being applied.It will be noted that the pull tab 74 is preferably at the forward endof the Web since it has been found that the area 78 near the trailingend of the adhesive bond will, at times, have an excessive amount ofadhesive deposited as the applicator wheel 30 breaks contact with theWeb 12. As seen in FIGURE 8, the adhesive pattern 72 usually has theenlarged end 78 as previously described. The forward end of the pattern72 comes to a point as at 80. Thus, it is much more satisfactory to pullthe tape from the leading end since initiation of tearing is easier andmore positive because of the narrow pointed end 80 in the adhesivepattern. If the tape is pulled from the end having the enlarged adhesivearea 78, there can be a tendency for tape breakage because of theenlarged bonded area.

The adhesive 24 can be selected from various hotmelt adhesives. Theseare bonding agents which achieve a solid state and resultant strength bycooling, as contrasted with other adhesives which achieve the solidstate through evaporation or removal of solvents. Prior to heating, ahot-melt adhesive is a thermoplastic, percent solid material, alladhesive. Application of heat brings the material to the liquid state,and after removal of the heat, it sets by simple cooling. The preferredadhesive for use in this invention is one which is solid and yetflexible at room temperature and which gradually softens to a fluidstage when heated. The adhesive becomes sufficiently hot and soft forapplication at a temperature of from about 375 F. to a maximumtemperature which will not damage either the adhesive, the tape materialor the packaging film. Preferably the adhesive is applied in atemperature range of from about 490 F. to about 510 F. Furthermore, thepreferred adhesive should be resistant to water, fats, oils, weak acidsand alkalis, and should be non-brittle and stronger than paperboard from-50 F. to +150 F. A hot-melt adhesive which has been foundsatisfactorily in practicing the present invention is sold by UnitedShoe Machinery Company under the trade name of Thermogrip Adhesive#1312.

Numerous hot-melt adhesives were examined in reducing the invention topractice. It was discovered that although many had similar properties,none were entirely satisfactory and consistent in making the bondbetween the film and the tear tape except the above-mentioned ThermogripAdhesive #1312. This adhesive was prepared in accordance with the methoddescribed in Example I of US. Patent 2,894,925 granted on July 14, 1959.The

composition of the adhesive was as follows:

Parts by weight Polyethylene having an average molecular weight of15,000 40 Butyl rubber copolymer of about 98 parts isobutylene and 2parts isoprene 25 B-pinene polymer resin-melting point C.

(Piccolite S-125) 35 Antioxidant 2 This adhesive was found verysatisfactory in adhering a 2 mil polyethylene web of packaging materialto a tear tape material composed of a three-layer laminate having anouter layer of .5 mil polyethylene terephthalate, an intermediate layerof .1 mil polyvinylidene chloride and another outer layer of .3 milpolyethylene. The polyethylene layer of the laminate was bonded to thepackaging material.

Referring again to FIGURE 2, the web 12 can be severed along the dottedlines 81, 82, and 84 to form individual packaging wrappers. For example,the wrapper 86 between the dotted lines 81 and 82 can be severed andsealed to form a package around objects such as the detergent tablets88, 90, 92 and 94 shown in FIG- URE 4. This package can be formed andcompleted by overlapping the edges 96 and 98 of the wrapper 86 and thenforming the vertical heat seal 100 when the web 12 is made from aheat-sealable thermoplastic material. Similarly, the ends of the packagecan then be finished by heat sealing the ends at 102 and 104.

In FIGURE 5, the finished package 106 is illustrated on the sideopposite the seal 100. It will be noted that the tear tape 68 is fullyexposed including the pull tab 74 since the package is formed so thatthe tear tape 68 is on an external surface when finished. FIGURE 6illustrates the package of FIGURE 5 after a pulling force has beenapplied to the pull tab 74 to partially remove the tear tape 68. Theadherence of the tape at the bond area 72 (FIGURE 3) is such that itcauses the removal of a narrow portion of the packaging material bymeans of clean and straight tears to form the slot 108. When the teartape has been fully removed, the full length of the slotl08 is exposedas shown in FIGURE 7. When the package is in this condition, theindividual articles can be very easily removed as will be apparent fromthe drawing.

Polyethylene and similar heat-sealable materials have a grain. Thesematerials can be formed into sheets or webs by an extrusion process. Theextrusion process plus the tensile load on the web when it is withdrawnfrom the extrusion die tends to orient the grain in the direction ofextrusion which is known in the art as the machine direction. In FIGURE2, the grain orientation of the polyethylene web 12 would be in thedirection of the arrow A. It will be noted that the tapes 68 and 70 areadhered with the long dimension of each substantially in the samedirection as the direction of grain orientation. It was found that theuse of an adhesive to adhere the tear tape as described herein willprovide a satisfactory opening device regardless of the direction ofgrain orientation in the packaging film with respect to the longdimension of the tear tape.

While particular embodiments of the invention have been illustrated anddescribed, it will be obvious to those skilled in the art that variouschanges and modifications can be made without departing from the spiritand scope of the invention and it is intended to cover in the appendedclaims all such changes and modifications that are within the scope ofthis invention.

What is claimed as new is:

1. A plastic package comprising a plastic packaging material sealed toenclose at least one article therein, a tear tape adhered to the outersurface of the plastic packaging material by means of a hotmelt adhesivecomposition applied as a bead along a narrow elongated area on theoutside surface of the plastic packaging material, said plasticpackaging material being of substantially uniform thickness throughoutits entire area including said narrow elongated area, the pulling andtearing force when applied to said tear tape being transmitted throughsaid bead to cause tearing of a narrow slot in said plastic packagingmaterial in the area of the bead thereby gaining access to the packagecontents.

2. A plastic package as described in claim 1 wherein said tear tapecomprises a three-layer laminate having an outer layer of polyethylene,an intermediate layer of polyvinylidene chloride, and an outer layer ofpolyethylene terephthalate, said polyethylene layer of said tear tapebeing adhered to said plastic packaging material.

3. A plastic package comprising a grained plastic packaging materialsealed to enclose at least one article therein, a tear tape adhered tothe outer surface of the plastic packaging material by means of ahot-melt adhesive composition applied as a bead along a narrow elongatedarea on the outside surface of the plastic packaging material,

said plastic packaging material being of substantially uniform thicknessthroughout its entire area including said narrow elongated area, saidnarrow elongated area being substantially in the same direction as thedirection of grain orientation of said plastic packaging material, thepulling and tearing force when applied to said tear tape beingtransmitted through said bead to cause substantially straight cleantears in the plastic packaging material in the direction of its grainorientation thereby gaining access to the package contents.

4. A plastic package as described in claim 3 wherein said tear tapecomprises a three-layer laminate having an outer layer of polyethylene,an intermediate layer of polyvinylidene chloride, and an outer layer ofpolyethylene terephthalate, said polyethylene layer of said tear tapebeing adhered to said plastic packaging material.

5. A plastic package comprising a plastic packaging material sealed toenclose at least one article therein, a tear tape adhered to the outersurface of the plastic packaging material by means of a hot-meltadhesive composition applied as a bead along a narrow elongated area onthe outside surface of the plastic packaging material, said plasticpackaging material being of substantially uniform thickness throughoutits entire area including said narrow elongated area, said adhesivecomposition having the characteristics of being solid and flexible atroom temperature, softening when heated to a range of from about 220 F.to 250 F. and being applied when heated to a temperature of from about375 F. to a temperature which will not cause damage to any of thepackage components comprising the adhesive, the plastic packagingmaterial and the tear tape material, the pulling and tearing force whenapplied to said tear tape being transmitted through said head to causetearing of a narrow slot in said plastic packaging material therebygaining access to the package contents.

6. A plastic package as described in claim 5 wherein said tear tapecomprises a three-layer laminate having an outer layer of polyethylene,an intermediate layer of polyvinylidene chloride, and an outer layer ofpolyethylene terephthalate, said polyethylene layer of said tear tapebeing adhered to said plastic packaging material.

7. A plastic package comprising a grained plastic packaging materialsealed to enclose at least one article therein, a tear tape adhered tothe outer surface of the plastic packaging material by means of ahot-melt adhesive composition applied as a bead along a narrow elongatedarea on the outside surface of the plastic packaging material, saidplastic packaging material being of substantially uniform thicknessthroughout its entire area including said narrow elongated area, saidadhesive composition having the characteristics of being solid andflexible at room temperature and softening when heated, and beingapplied when heated to a temperature of from about 375 F. to atemperature which will not cause damage to any of the package componentscomprising the adhesive, the plastic packaging material and the teartape material, said narrow elongated area being substantially in thesame direction as the direction of grain orientation of said plasticpackaging material, the pulling and tearing force when applied to saidtear tape being transmitted through said bead to cause substantiallystraight clean tears in the plastic packaging material thereby gainingaccess to the package contents.

8. A plastic package as described in claim 7 wherein said tear tapecomprises a three-layer laminate having an outer layer of polyethylene,an intermediate layer of polyvinylidene chloride, and an outer layer ofpolyethylene terephthalate, said polyethylene layer of said tear tapebeing adhered to said plastic packaging material.

9. A plastic package comprising a plastic packaging material sealed toenclose at least one article therein, a tear tape adhered to the outersurface of the plastic packaging material by means of a hot-meltadhesive composition applied along a narrow elongated area on theoutside surface of the plastic packaging material, said plasticpackaging material being of substantially uniform thickness throughoutits entire area including said narrow elongated area, the tear tapeincluding a pull tab at one of its extremities, said narrow elongatedadhesive area being tapered, said tear tape being adhered to the plasticpackaging material such that the pull tab projects from the narrower endof the adhesive area, said tear tape being capable of tearing open saidplastic packaging material when a pulling force is applied to the teartape whereby the plastic packaging material is severed to gain access toan article in the package.

10. A plastic package comprising a grained plastic packaging materialsealed to enclose at least one article therein, a tear tape adhered tothe outer surface of the plastic packaging material by means of ahot-melt adhesive com position applied along a narrow elongated area onthe outside surface of the plastic packaging material, said plasticpackaging material being of substantially uniform thickness throughoutits entire area including said narrow elongated area, said narrowelongated area being substantially in the same direction as thedirection of grain orientation of said plastic packaging material, thetear tape including a pull tab at one of its extremities, said narrowelongated adhesive area being tapered, said tear tape being adhered tothe plastic packaging material such that the pull tab projects from thenarrower end of the adhesive area, said tear tape being capable oftearing open said plastic packaging material when a pulling force isapplied to the tear tape to provide a substantially straight clean tearin the plastic packaging material in the direction of its grainorientation whereby the plastic packaging material is severed to gainaccess to an article in the package.

11. A plastic package comprising a plastic packaging material sealed toenclose at least one article therein, a tear tape adhered to the outersurface of the plastic packaging material by means of a hot-meltadhesive composition applied along a narrow elongated area on theoutside surface of the plastic packaging material, said plasticpackaging material being of substantially uniform thickness throughoutits entire area including said narrow elongated area, said adhesivecomposition having the characteristics of being solid and flexible atroom temperature, softening when heated to a range of from about 220 F.to 250 F. and being applied when heated to a temperature of from about375 F. to a temperature which will not cause damage to any of thepackage components comprising the adhesive, the plasticpackagingmaterial and the tear tape material, the tear tape including apull tab at one of its extremities, said narrow elongated adhesive areabeing tapered, said tear tape being adhered to the plastic packagingmaterial such that the pull tab projects from the narrow end of theadhesive area, said tear tape being capable of tearing open said plasticpackaging material when a pulling force is applied to the tear tapewhereby the plastic packaging material is severed to gain access to anarticle in the package.

12. A plastic package comprising a grained plastic packaging materialsealed to enclose at least one article therein, a tear tape adhered tothe outer surface of the plastic packaging material by means of ahot-melt adhesive composition applied along a narrow elongated area onthe outside surface of the plastic packaging material, said plasticpackaging material being of substantially uniform thickness throughoutits entire area including said narrow elongated area, said adhesivecomposition having the characteristics of being solid and flexible atroom temperature and softening when heated, and being applied whenheated to a temperature of from about 375 F. to a temperature which willnot cause damage to any of the package components comprising theadhesive, the plastic packaging material and the tear tape materiak saidnarrow elongated area being substantially in the same direction as thedirection of grain orientation of said plastic packaging material, thetear tape including a pull tab at one of its extremities, said narrowelongated adhesive area being tapered, said tear tape being adhered tothe plastic packaging material such that the pull tab projects from thenarrow end of the adhesive area, said tear tape being capable of tearingopen said plastic packaging material when a pulling force is applied tothe tear tape to provide a substantially straight clean tear in theplastic packaging material whereby the plastic packaging material issevered to gain access to an article in the package.

References Cited UNITED STATES PATENTS 2,554,160 5/1951 Von Gunten229--51 2,946,434 7/ 1960 Brina 229-5 1 3,098,601 7/1963 Anderson et al229-51 3,191,507 6/1965 Cowie 22951 3,166,234 1/1965 Amberg 22951FOREIGN PATENTS 625,351 6/1949 Great Britain.

R. PESHOCK, Assistant Examiner.

